Cleomenes I in the context of "Darius the Great"

Cleisthenes (/ˈklaɪsθɪniːz/ KLYS-thin-eez; Ancient Greek: Κλεισθένης), or Clisthenes (c. 570 – c. 508 BC), was an ancient Athenian lawgiver credited with reforming the constitution of ancient Athens and setting it on a democratic footing in 508 BC. For these accomplishments, historians refer to him as "the father of Athenian democracy". He was a member of the aristocratic Alcmaeonid clan. He was the younger son of Megacles and Agariste making him the maternal grandson of the tyrant Cleisthenes of Sicyon. He was also credited with increasing the power of the Athenian citizens' assembly and for reducing the power of the nobility over Athenian politics.

In 510 BC, Spartan troops helped the Athenians overthrow the tyrant Hippias, son of Peisistratus. Cleomenes I, king of Sparta, put in place a pro-Spartan oligarchy headed by Isagoras. However, Cleisthenes, with the support of the middle class and aided by democrats, took over. Cleomenes intervened in 508 and 506 BC, but could not stop Cleisthenes and his Athenian supporters. Through Cleisthenes' reforms, the people of Athens endowed their city with isonomic institutions—equal rights for all citizens (though only free men and women were citizens)—and established ostracism as a punishment.

Isagoras (Ancient Greek: Ἰσαγόρας), son of Tisander, was an Athenian aristocrat in the late 6th century BC.

He had remained in Athens during the tyranny of Hippias, but after Hippias was overthrown, he became involved in a struggle for power with Cleisthenes, a fellow aristocrat. In 508 BC he was elected archon eponymous, but Cleisthenes opposed him, with support from the majority of the population. Isagoras requested support from the Spartan king Cleomenes I, an old friend who had earlier been given hospitality by Isagoras. According to Herodotus, Cleomenes had had an affair with Isagoras's wife.

Hippias (Ancient Greek: Ἱππίας, romanized: Hippías; c. 570 BC – 490 BC) was the last tyrant of Athens, ruling from 527 to 510 BC. He was one of the Peisistratids, a group of tyrants from the same family in ancient Greece. His father was Pisistratus, who preceded him as ruler of Athens, while his brother Hipparchus may have ruled jointly with him. Hippias also had an illegitimate son, Hegesistratus, whom he made tyrant of Sigeion. He was deposed when Cleomenes I of Sparta successfully invaded Athens and forced him to flee to the Achaemenid Empire.

Leonidas I (/liəˈnaɪdəs, -dæs/; Ancient Greek: Λεωνίδας, Leōnídas; born c. 540 BC; died 11 August 480 BC) was king of the Ancient Greek city-state of Sparta. He was the son of king Anaxandridas II and the 17th king of the Agiad dynasty, a Spartan royal house which claimed descent from Heracles. Leonidas I ascended to the throne in c. 489 BC, succeeding his half-brother king Cleomenes I. He ruled jointly along with king Leotychidas II until his death in 480 BC, when he was succeeded by his son, Pleistarchus.

At the Second Greco-Persian War, Leonidas led the allied Greek forces in a last stand at the Battle of Thermopylae (480 BC), attempting to defend the pass from the invading Persian army, and was killed early during the third and last day of the battle. Leonidas entered myth as a hero and the leader of the 300 Spartans who died in battle at Thermopylae. While the Greeks lost this battle, they were able to expel the Persian invaders in the following year.

Leotychidas II (Ancient Greek: Λεωτυχίδας; Doric: Λατυχίδας Latychidas; c. 545 – c. 469 BC) was king of Sparta from 491–476 BC, alongside Cleomenes I and later Leonidas I and Pleistarchus. He led Spartan forces during the Persian Wars from 490–478 BC.

Born in Sparta around 545 BC, Leotychidas was a descendant of the Royal House of the Eurypontids (through Menamus, Agesilaus, Hippocratides, Leotychides, Anaxilaus, Archidamos, Anaxandridas I and Theopompus) and came to power in 491 BC with the help of the Agiad King Cleomenes I by challenging the legitimacy of the birth of Demaratus for the Eurypontid throne of Sparta. Later that year, he joined Cleomenes's second expedition to Aegina, where ten hostages were seized and given to Athens. However, after Cleomenes's death in 488 BC, Leotychidas was almost surrendered to Aegina.

Anaxandridas II (Ancient Greek: Ἀναξανδρίδας, meaning "descendant of Anaxander") was an Agiad king of Sparta from c. 560 BC to 524 BC, father of Leonidas I and grandfather of Pleistarchus. Under the leadership of the ephor Chilon, in office during the middle of the 6th century, Sparta ended its streak of violent conquests, such as in Messenia, and adopted a pro-Achaea policy based on diplomacy. Anaxandridas was succeeded by Cleomenes I.